Rear Disc - Locking rear wheels

[nicbeer]

Hey all.

I have seen this discussed before in varying degrees of success.

I would like this to be tech of after installs not how to install them or what are they. (search is for that)

I have the WT Zook, 1.6 vented brakes up front, 1yold master cyl, and orig sierra discs and calipers on the back with custom brackets. handbrake is on the transfer.

In the dry it stops very quick, but still locks the rears up. in the wet downright dangerous with rear steer on heavy breaking. can be fun on the gravel/dirt fast corners but onroad i am worried about.

what have people done to stop this happening. so far setup is stock cept for the discs.

I have a brake proportioning valve here i can put in to reduce the rear line pressure but interested in hearing others that have worked.

Nic

[bazooked]

im afraid the only longterm solution is the valve.

[joeblow]

done heaps of non handbrake setups at the back...first mistake people make is to use sierra callipers..way too big for the rear. legally you are not allowed to put an adjustable valve in the sytem. the other way is to use an lspv set-up.for half decent braking the rear pad area has to be a minimum of %25 smaller, that way no valves should be needed.

[nicbeer]

hrmm

Joe - is there any calipers that utilise the same mounts as sierra ones? i.e to swap them over?

afaik u can use a valve but must be under a cover and cannot be used whilst driving.

i was thinking of putting it either in front of front seat on the hump and use some braided lines down to chassis or under the master cylinder and use some U shaped lines.

What is a lspv setup? i already have the std valve in the back still from factory but not touched that at all.

[MART]

Nic , front zuk callipers are to big for rears but with a bias valve , 70/30 it will work well , the valve cannot be in the cab and must have a cover to prevent it being adjusted only with the use of tools , just plumb it into the rear line , they are legal in NSW as I have mine engineered , mine is of a R type mustang but can be purchased in most performance shops , not sure if any other callipers will fit , if you do change them you will need new mounts , Cheers Paul.

[joeblow]

lspv- load sensing proportioning valve. is what vits and jimnys have on the arse to adjust brake proportioning for load.pain in the bum to set-up!

[want33s]

What is a lspv setup?

LSPV= Load Sensitive Proportioning Valve... As fitted standard to lots of utes.. EG: Hilux and Holden 1 tonner.
It increases brake power to the rear when more weight is applied to rear of car, or rather decreases it when empty.
EDIT:Beat me!

[nicbeer]

thx. just found it on the net.

i have a valve to install here.

MART, got any pics of urs mounted up.

[11_evl]

a mate of mine just bought the vitara set up from lowrangeoffroad and all it had in the kit to overcome it was a TAP style valve that you just adjust to suit. also come with adaptors and Ushape pipes so no cutting was needed.. it hasnt been installed so dont no how it all goes.
on the invoice the valve and pipes and fittings was $71. the whole invoice price, with other brake parts, was somthing cheap like $330 with a HD vit idler arm kit. not relevent in this case but still worth a mention for people reading wanting to do disc conversion

[christover1]

I have heard some people turn down the discs, thus achieving less braking area on the disc.
This sounds dodgy to me and would unlikely be legal or successful???
My rears are from the rear of a Pintara/Skyline.
I believe that may be why I don't have bias issues?
Mine is a 1.0 litre master, no power assist.

There's a spring/valve thing in master that needs removing, so you don't get a problem with constant pressure on rears.
This could cause an issue?

Some also use better pads in front than in the rear to help with biassing issues.

christover

[nicbeer]

There's a spring/valve thing in master that needs removing, so you don't get a problem with constant pressure on rears.
This could cause an issue?

christover

Have heard of this one. (is this the master or std rear prop valve on chassis rail?)

Is this apparent for all the zook Drum brakes? (WT and NT) also, anyone else done this in theres and which spring is it?

[christover1]

There's a spring/valve thing in master that needs removing, so you don't get a problem with constant pressure on rears.
This could cause an issue?

christover

Have heard of this one. (is this the master or std rear prop valve on chassis rail?)

Is this apparent for all the zook Drum brakes? (WT and NT) also, anyone else done this in theres and which spring is it?

I can only answer for mine. 83 lwb 1.0.
It never had a rear valve or the split lines of the 1.3's.
Mine has only 1 single line from master to rear end, (1 to front which gets split shortly after, to each front only) and the valve was in the master, just behind where pipe screws in. (ON mine front part of master goes to rear end)
I just unscrewed the line, flipped out a bit of plastic with a light spring on it, then re fitted, and rebled system.
It may not even exist for later models?
And could be in another place?

christover

[joeblow]

the valve your talking about criss is a brake residual valve.this keeps some slight outwards pressure on the drum brakes. will not do anyting for brake bias. and always remove if your zook once had all drums....and now has all discs.

[christover1]

the valve your talking about criss is a brake residual valve.this keeps some slight outwards pressure on the drum brakes. will not do anyting for brake bias. and always remove if your zook once had all drums....and now has all discs.

I found this out after I destroyed the first set of pads in under a month
Now they are lasting 6months to a year, depending on how much use/mud they get.

[nicbeer]

the valve your talking about criss is a brake residual valve.this keeps some slight outwards pressure on the drum brakes. will not do anyting for brake bias. and always remove if your zook once had all drums....and now has all discs.

Joe - what part are u talking about (same as chris?) and are these in the WT ones also. if they are i will remove when i do the bias valve. i am waiting on some hoses to be made.

Is it ok to hook up the bias valve by stainless flex hose? either to the existing line or the master?

[joeblow]

they were only in sierra's with 4 wheel drums and no booster, anything with factory front discs won't have this item.

[hyzook]

I have the same braking set up although I have Vit Estate discs, calipers and master cyl. I have a proprtioning valve on mine which is engineered is NSW. After some adjusting over a short period of different driving conditions it all good now.

[11_evl]

thats the one in the lowrange kit. hows it work?? all good??

[BenT]

I have the same braking set up although I have Vit Estate discs, calipers and master cyl. I have a proprtioning valve on mine which is engineered is NSW. After some adjusting over a short period of different driving conditions it all good now.

Looks like you have fitted the Vit master cyl AND booster... how does that go? I assume the booster is bigger diameter than std? What is the master cylinder bore size?

How do you get on for battery clearance to the booster?

Much work to fit?

I hear the coily boosters are also 1" bigger dia, but I don't know if they bolt up.

Ben

[hyzook]

thats the one in the lowrange kit. hows it work?? all good??

I got it from Spidertrax with the disc conversion kit and after setting its now great.

I have the same braking set up although I have Vit Estate discs, calipers and master cyl. I have a proprtioning valve on mine which is engineered is NSW. After some adjusting over a short period of different driving conditions it all good now.

Looks like you have fitted the Vit master cyl AND booster... how does that go? I assume the booster is bigger diameter than std? What is the master cylinder bore size?

How do you get on for battery clearance to the booster?

Much work to fit?

I hear the coily boosters are also 1" bigger dia, but I don't know if they bolt up.

Ben

Yes sorry, AND booster which is a larger diameter. while the bolt pattern on the firewall is the same the centre hole in the firewall had to enlarged slightly which was not much fun, battery clearance is tight but I still fit a decent size battery after some cutting of anything that wasn't structural. I am not sure of the master cyl bore size, Its all off a 4 door vit as I wanted the ventilated discs.

[nicbeer]

sweet pic hyzook.

is that mounted at all there or floating off the pipes?

i am planning to mount mine about 100mm off the block down from the master and inline with it so need two new hard lines made. getting them 2morrow.

is it ok to use a stainless flexible for the master to valve? or on other side at all.

[hyzook]

sweet pic hyzook.

is that mounted at all there or floating off the pipes?

i am planning to mount mine about 100mm off the block down from the master and inline with it so need two new hard lines made. getting them 2morrow.

is it ok to use a stainless flexible for the master to valve? or on other side at all.

Its just floating, The flex hose I am not sure, best speak with a brake expert.

[lexplay]

how did u go nic did you get the pipes on last night? were the ends right?

[MightyMouse]

Another rougher option is to remove some of the pad area - its not that hard to do with a angle grinder or milling machine - however its messy !

Just to be sure - I don't mean thickness or the backing plate, just the area.

Remove 20% of the pad friction material area - decrease braking by approx 20%. Obviously remove material from the friction materials ends first and should be done "sensibly" ( 90 removed is not good ! ) but you can do it a bit at a time till its right with old pads so as not to cost too much.

Whilst this works, you need to do it with every set of replacement pads you install so its not fit and forget forever.

[nicbeer]

Lex - yeh ends look good.

didnt get time last nite to fit it up. looks like either tonite or friday to play with it.

MM - yeh have heard of that also but cant be arsed doing that each time and i am guessing reducing the pad area will make them wear quicker.

also do u have opinion on flexible hoses for this application? i would guess they are fine as the there are flexy lines only below it not far.

[Mike_1324]

Another rougher option is to remove some of the pad area - its not that hard to do with a angle grinder or milling machine - however its messy !

Just to be sure - I don't mean thickness or the backing plate, just the area.

Remove 20% of the pad friction material area - decrease braking by approx 20%. Obviously remove material from the friction materials ends first and should be done "sensibly" ( 90 removed is not good ! ) but you can do it a bit at a time till its right with old pads so as not to cost too much.

Whilst this works, you need to do it with every set of replacement pads you install so its not fit and forget forever.

I had too much braking on the rear of the race bike, and so i tried this, but found the exact oppisite....

By reducing the friction area, you still have the same force over a smaller area, so it was biteing, and causing more issues, by having a bigger area, you can put less force over a larger area...

Just a thought.

Mike

[MightyMouse]

Pad and disk materials are different on bikes, but I can understand where your coming from with biting.

However varying the pad area is exactly how brake developers fine tune systems as its much easier than caliper/piston changes.

As for your area pressure isssue, same pedal effort ( line pressure ) is applied to the font and rear, but because there's now a greater difference in pad areas there's a bigger bias difference.

So If its a fine tune, done with old pads - what's to loose ?

[nicbeer]

Ok valve is in now. Adj to min pressure and seems a lot better on hard braking but can still lock rears if stamp on pedal on dry road. Sound about right? I am guessing the valve only cuts a certain pressure out.

only done 1 test or so, so far.

Hyzook - whats urs adjusted too.

MM - When people say taking material off, is this cuttin slots in the pad or taking the thickness down?

[Gwagensteve]

It'll be slots not thickness.

The idea is to reduce the area of the pad.


I'm interested to see how this works out, I'm going to sierra front calipers in the rear of mine soon. I know it will have its problems but it is by far the neatest setup for what I want to achieve.

Steve.

[MightyMouse]

MM - When people say taking material off, is this cuttin slots in the pad or taking the thickness down?

Its slots as Steve indicated - the idea in general terms is to leave the friction area as long as possible ( to avoid pad "tip" ) and reduce its height. This can also be done by machining.

This keeps the pad stable when pressure is applied.

Reducing the friction material thickness does nothing except shorten the pad life.